The present invention relates to an improvement in the creation and modification of graphical images on a computer screen or the like and, in particular, to a method for changing a characteristic function of an icon or tool with a cursor movement device or stylus.
One such tool often present in a computer graphics system is an eraser. In a computer graphics system, one of the more common methods of erasing parts of graphical images on a screen is by performing an erasure function using a cursor movement device, such as a mouse or a stylus with an electronic tablet. For instance, in U.S. Pat. No. 4,633,436 to Flurry (hereby incorporated by reference), a real-time erasing feature is described. In this method, user input via an electronic tablet and stylus combination is stored in a point list. When the disclosed system is placed in an erasing mode, the display screen is divided into a number of smaller grid boxes. Only grid boxes touched by the stylus are searched for erasure (and subsequent deletion from the point list).
Typically, the cursor is provided in the form of a graphical icon. For example, in the MacPaint.RTM. graphics program manufactured by Apple.RTM. Computer, Inc., the eraser icon resembles a chalkboard eraser. U.S. Pat. No. 4,823,285 to Blancato (hereby incorporated by reference) describes such a system. The erasing width of the eraser is usually constant, which may be too large when fine erasing is needed or too narrow when large portions of a graphical image are to be erased.
In some applications, the erasing width of the eraser can be changed using an external input device, such as a keyboard. Switching between modes using a keyboard can be tedious and impedes the process of freehand drawing. Also, most erasers have the same orientation at all times. This can make it difficult to precisely erase regions of a graphical image that cannot be reached by an effective point of the eraser. For example, if the eraser were to have an upright square shape, it would be difficult to erase a corner of a square graphical image not properly aligned with the eraser.
Accordingly, there is a need for a method which allows a user to quickly change the erasing width of a graphical eraser. There is also a need for a method which allows the user to quickly change the orientation of a eraser in a graphical drawing environment. More broadly, with respect to tools which are used for modifying an image, there is a need for a method which allows a user to quickly change the characteristics of the tool.